The fandisc consists of the following: Houzuki’s chapter, the epilogues for the original game’s heroines, and a hidden omake.

For starters, Houzuki’s chapter will probably tie everything that was left unanswered in Himawari no Shoujo. Therefore, it is really a step that any reader shouldn’t skip, considering how it is canonically ending everything so far.
Houzuki’s chapter sets the timeframe many years before the events of Himawari, at the very same location. Akutsu Masaomi and Higuchi Saburou, the 2 protagonists of the story managed to survive from the hellish SHCP trial and enter in the final part of their examination.
They soon meet the current SHCP in charge of the town, Ari Ruruliant Houzuki. Cunning and often plotting behind their back, Ari will monitor them as the two will be in charge of Saika Miina, the only student with an obligation at that given time.
Masaomi progressively realize that Miina’s situation is completely irrational, but many obstacles will arise before him.

“Sharin no Kuni, Yuukyuu no Shounenshoujo” related links:

Sharin no Kuni, Himawari no Shoujo
Sharin no Kuni, Yuukyuu no Shounenshoujo HCG